Sunflowers and radioactivity I read yesterday that sunflowers were used and to cleanup radioactivity at Chernobyl and the Atomic Bomb sites in Japan and may be used as part of a campaign to clean up the Fukushima area.  
But my questions are:


*

*How does a sunflower absorb radioactivity?

*Is there a way to measure how well the sunflowers are working? 

*Can sunflowers planted in not particularly radioactive places concentrate otherwise harmless radiation?


I was tempted to ask this on Skeptics.SE, but there's not much to be skeptical about, except whether or not it's a good idea 
 A: It may have something to do with the growth rate of sunflowers.  During peak growing times sunflowers can grow inches in a single day, which likely results in them drawing more water out of the ground, allowing them to concentrate the radioactive materials through deposition in the plant matter at a faster rate than other plant organisms.  I would suspect you could monitor the process with standard instruments, which are pretty sensitive to the presence of particle decay. I doubt that there is any serious risk of activity accrual in areas that are not already contaminated.
Edited to add:
A quick search on the Google points out that sunflowers are good at absorbing heavy metals via rhizofiltration. 
A: *

*As your second link states, sunflowers absorb ions from the soil. That's how they get nutrients to grow, but the same chemical mechanism will absorb cesium atoms - cesium is very soluable in water. The explosion at Fukushima ejected two isotopes with a particular danger to humans, 137Cs (cesium) and 131I (Iodine) Because the latter has a half-life of only 8 days 135Cs is currently the main cause of radioactivity in the area. Therefore, sunflowers grown in the Fukushima area will absorb the radioactive Cesium-137 isotope.

*The effect is quite easy to measure: the sunflowers themselves become radioactive because they contain radioactive Cesium-137 atoms. In particular, Cesium-137 gives off characteristic gamma rays through the decay via Barium-137m.

*Not really. Banana's are far more effetive in that respect.
